We survived a winter in north Georgia, lowest temp of 18F and snow, in a '96 Jayco TT without any real difficulty other than this Florida boy freezing his patootie off.
I gather you'll actually occupy the rig rather than just park it unoccupied.
Our Jayco had some sort of covering on the bottom but tanks were exposed. We tried a heated water hose but the actual fitting into the trailer froze. Then someone drove over a water line and that night the check valve inside the fitting froze in the closed position and jammed forever, so we removed it. On really cold nights lower than about 28F we disconnected the water hose and operated off the tank, then refilled the tank when the hose thawed out.
We didn't do anything special with the waste tanks or sewer hose and just left the black tank valve closed and the grey tank valve open as normal. The hose would freeze occasionally but since the grey tank was empty it would thaw long before the grey tank would have filled up. We did make sure to not be caught with a full black tank and a frozen hose.
We ran the furnace to stay nice and warm inside. Of course we went through lots of propane; since this trailer wasn't going anywhere we had the local gas company install a 100-gallon residential tank and as a bonus bought gas at the residential rate rather than the higher recreational rate. Although the area beneath the floor wasn't specifically heated, the furnace was ducted under the floor and provided enough heat to prevent freezing.
One very important thing we did was cover the windows inside with plastic film. This is a very thin film that's taped all around the window, then shrunk with heat from a hair dryer. What it does is prevent moisture from condensing on the cold glass and wetting down the interior walls.
Fast-forward a few years and last winter we went through a freezing rain/ice storm near the tropical paradise of Mayo, Fla., lowest tamp 22F.
We're in a motorhome with enclosed tanks/plumbing but again the tanks aren't specifically heated.
We did the usual thing of disconnecting the water hose, but the twist this time is that in the wee hours the power went out. The furnace pulled the house batteries way down so we ran the generator. After several hours the generator died so we resorted to running the engine so we could run the furnace and charge the house batteries.
Turned out that the 25-year-old propane-fuelled generator chose that night to plug up with the oil and gunk that's in all propane.
But we did come through with no damage at 22F. We weren't expecting that cold so didn't have any window film and actually got a little ice on the inside of the windows and windshield.
It was amazing to be in Florida and seeing sheets of ice and icicles coating the sides of the rig, toad etc. I'd lived in Leon and Wakulla counties earlier but had never seen anything like this.
I think the main reason we didn't have any frozen plumbing with either rig is that we ran the furnace and we ran it warm; no 60F indoors for us. So that heated the underneath and walls enough to prevent freezing. An electric space heater wouldn't have done that. We did use a space heater during the days but cranked up the furnace for the nights.
That's our experience and your mileage may vary. If in doubt, winterize. It doesn't take long to do it or undo it.
BTW, we're spending this winter back in central Florida!
-jbh-
